Suppressive and enhancing effects in early visual cortex during illusory shape perception: A comment on.

Moors P - Iperception (2015)

Bottom Line:
In a recent functional magnetic resonance imaging study, Kok and de Lange (2014) observed that BOLD activity for a Kanizsa illusory shape stimulus, in which pacmen-like inducers elicit an illusory shape percept, was either enhanced or suppressed relative to a nonillusory control configuration depending on whether the spatial profile of BOLD activity in early visual cortex was related to the illusory shape or the inducers, respectively.The authors argued that these findings fit well with the predictive coding framework, because top-down predictions related to the illusory shape are not met with bottom-up sensory input and hence the feedforward error signal is enhanced.Conversely, for the inducing elements, there is a match between top-down predictions and input, leading to a decrease in error.

ABSTRACTIn a recent functional magnetic resonance imaging study, Kok and de Lange (2014) observed that BOLD activity for a Kanizsa illusory shape stimulus, in which pacmen-like inducers elicit an illusory shape percept, was either enhanced or suppressed relative to a nonillusory control configuration depending on whether the spatial profile of BOLD activity in early visual cortex was related to the illusory shape or the inducers, respectively. The authors argued that these findings fit well with the predictive coding framework, because top-down predictions related to the illusory shape are not met with bottom-up sensory input and hence the feedforward error signal is enhanced. Conversely, for the inducing elements, there is a match between top-down predictions and input, leading to a decrease in error. Rather than invoking predictive coding as the explanatory framework, the suppressive effect related to the inducers might be caused by neural adaptation to perceptually stable input due to the trial sequence used in the experiment.

Mentions:
In a recent study, Kok and de Lange (2014) sought to test these predictions using the well-known Kanizsa illusory shape stimulus (Figure 1A). In this stimulus, pacmen-like inducers give rise to an illusory shape percept, perceived as a foreground figure relative to the inducers in the background (Kanizsa, 1979; Kogo & Wagemans, 2013; Wagemans et al., 2012). Within the proposed framework, the authors predicted that neural activity in early visual cortex related to the inducers should go down, because top-down predictions match the bottom-up sensory input. However, the reverse should hold for neural activity related to the illusory shape. That is, the top-down predictions would signal a shape whereas none is to be found in the sensory signal.

Mentions:
In a recent study, Kok and de Lange (2014) sought to test these predictions using the well-known Kanizsa illusory shape stimulus (Figure 1A). In this stimulus, pacmen-like inducers give rise to an illusory shape percept, perceived as a foreground figure relative to the inducers in the background (Kanizsa, 1979; Kogo & Wagemans, 2013; Wagemans et al., 2012). Within the proposed framework, the authors predicted that neural activity in early visual cortex related to the inducers should go down, because top-down predictions match the bottom-up sensory input. However, the reverse should hold for neural activity related to the illusory shape. That is, the top-down predictions would signal a shape whereas none is to be found in the sensory signal.

Bottom Line:
In a recent functional magnetic resonance imaging study, Kok and de Lange (2014) observed that BOLD activity for a Kanizsa illusory shape stimulus, in which pacmen-like inducers elicit an illusory shape percept, was either enhanced or suppressed relative to a nonillusory control configuration depending on whether the spatial profile of BOLD activity in early visual cortex was related to the illusory shape or the inducers, respectively.The authors argued that these findings fit well with the predictive coding framework, because top-down predictions related to the illusory shape are not met with bottom-up sensory input and hence the feedforward error signal is enhanced.Conversely, for the inducing elements, there is a match between top-down predictions and input, leading to a decrease in error.

ABSTRACTIn a recent functional magnetic resonance imaging study, Kok and de Lange (2014) observed that BOLD activity for a Kanizsa illusory shape stimulus, in which pacmen-like inducers elicit an illusory shape percept, was either enhanced or suppressed relative to a nonillusory control configuration depending on whether the spatial profile of BOLD activity in early visual cortex was related to the illusory shape or the inducers, respectively. The authors argued that these findings fit well with the predictive coding framework, because top-down predictions related to the illusory shape are not met with bottom-up sensory input and hence the feedforward error signal is enhanced. Conversely, for the inducing elements, there is a match between top-down predictions and input, leading to a decrease in error. Rather than invoking predictive coding as the explanatory framework, the suppressive effect related to the inducers might be caused by neural adaptation to perceptually stable input due to the trial sequence used in the experiment.